This invention relates generally to tufting apparatus for producing patterned textile goods such as carpet, upholstery, and the like, and more particularly to tufting apparatus having a yarn exchanger associated with each needle, at the inlet of which a plurality of yarns await the selective transportation of one such yarn to the needle and to which the yarn is subsequently retracted from the needle.
U.S. Pat. No. 4,549,496 which issued Oct. 29, 1985, to Kile discloses highly advantageous tufting apparatus for producing patterned tufted goods using yarns of different colors or different textures. This apparatus is capable of placing yarn into a backing to create patterns and designs which previously were generally available only from a weaving loom or by using printing techniques. The patented apparatus employs multiple heads spaced across the width of a backing material. Each head comprises a reciprocating hollow needle or backing opener tube for penetrating the backing and for implanting yarn tufts in the backing by feeding yarn through the needle pneumatically. The needle is connected to a yarn exchanger into which a plurality of yarns of different colors, for example, are supplied, and a mechanism is included which enables the selection of one or more of the yarns for implantation into the backing for each penetration by the needle. The multiple heads are stepped in synchronism across the backing for a distance corresponding to the spacing between the heads in order to implant a transverse row of yarn tufts. The backing is then advanced to the position of the next row and the process is repeated to implant the next row. A computer controls the selection of the yarn implanted by each backing opener for each penetration of the backing in order to produce a desired pattern in the finished goods.
A significant factor influencing the production speed of practical apparatus embodying the invention of the Kile patent is the number of tufting heads embodied in the apparatus. The greater the number of heads, the less distance each head must traverse and, accordingly, the faster a row of tufts can be implanted in the backing. As the number of heads increases, however, other problems arise. The increased weight makes it more difficult to move the heads accurately and to maintain their alignment and positions relative to one another. Thus rather than the multiple heads which carry the hollow needle being moved across the backing, Ingram U.S. Pat. No. 4,991,523 discloses the backing rather than the heads being shifted transversely to move substantially less weight transversely. This not only simplifies the transverse shifting apparatus but also provides greater speed and accuracy to the yarn placement.
Another significant factor influencing the cost and accuracy of such tufting apparatus is the control over the feeding of the yarn to the hollow needle. The feeding of the yarn must be positive, and when a yarn change is to be made for a particular needle the yarn previously stitched by that needle should be positively withdrawn from the needle so that the subsequent yarn will not be blocked by the previously sewn yarn. Unless this withdrawal of the previously sewn yarn is assured, a substantially greater air pressure is required to supply the subsequent yarn through the needle. Further more, when the yarn is withdrawn from the needle, unless the yarn withdrawal is controlled, the next time that yarn is required to be fed to the needle an accurate and consistent length of yarn cannot be assured. This would also result in requiring additional pressure to assure that a sufficient length of yarn is supplied. The effect is that a larger than required amount of pressure must be utilized, and if too much yarn is supplied to the needle additional yarn shearing operations are required for producing a satisfactory product.
This problem was solved by the apparatus disclosed in Ingram U.S. Pat. No. 5,080,028. There a pullback mechanism is disposed between a yarn feed roller and the hollow needle, the pullback mechanism acting to pull the yarn a preselected amount from the needle so that the yarn passageway in the needle is not restricted by the previous yarn when a subsequent yarn is to be sewn. Additionally, to assure that the pullback mechanism draws yarn from the needle and not from the yarn supply or the feed roller, clamping apparatus is disposed between the yarn feed roller and the pullback mechanism for positively clamping the yarn when a yarn change is to be made. The pullback mechanism is thereafter activated and the yarn feed roller ceases positive feeding of the yarn. Thus, the yarn pullback mechanism draws a predetermined amount of yarn from the needle maintaining it in reserve until again required. Additionally, the yarn feed roller as it ceased positive feeding draws a preselected amount of yarn from the yarn supply for immediate subsequent use when needed. When the needle is to commence stitching with a particular yarn, the yarn feed roller is activated and the yarn clamping apparatus and yarn pullback mechanism are deactivated.
A further significant factor effecting the efficiency and cost of the aforesaid apparatus and its operation is the amount of pressurized air that must be supplied to feed a selected yarn through the system from the one or two yarn ejectors which receive all of the yarn associated with the respective needle and direct the yarn through separate passageways to the yarn exchanger. The efficiency of this system can also effect the appearance of the product. In the aforesaid U.S. Pat. No. 4,549,496 air was supplied to a plenum from which the air was directed to a tapered space leading into each yarn carrying conduit extending to the yarn exchanger. Air was thus constantly supplied to the plenum under high pressure to drive the yarn fed by the yarn feed rollers. This resulted in a substantial amount of wasted air and the system was modified. As described in the aforesaid U.S. patent application, air flow is regulated and controlled so that air under a high pressure is only supplied to a passageway having the selected yarn for ejection into and through the needle, while air under a low pressure is supplied to the other passageways. This not only reduces the air requirements but provides better control of the yarn fed to the needle and permits the system to be quick acting. One problem that results, however, probably due to both the low and high pressure air flowing into the funnel shape of the yarn exchanger resulting in turbulence or a swirling action is that the various yarns can become tangled in the yarn exchanger at the inlet to the needle resulting in a clogging of the needle. When this occurs that needle becomes clogged and cannot feed yarn therethrough, i.e., it stops sewing yarn. The present invention is directed toward an effective and efficient solution to this difficulty.